Don't start netconsole by default

Netconsole startup fails with the default configuration. netconsole
is started by ovirt-post if configured and by defaults.Netconsole()
when configured on a running system. Don't start it in ovirt-post
if the configuration looks invalid.

Change-Id: Ib7ff7a4789bbc533f68f4aebf7ef851ddc6700b0
Signed-off-by: Ryan Barry <rbarry@redhat.com>
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=991353